U.S. patent application number 16/086567 was filed with the patent office on 2019-04-04 for multi-led system.
The applicant listed for this patent is EPCOS AG. Invention is credited to Sebastian Brunner, Thomas Feichtinger, Edmund Payr, Gunter Pudmich, Stephan Steinhauser.
Application Number | 20190103384 16/086567 |
Document ID | / |
Family ID | 59814554 |
Filed Date | 2019-04-04 |
United States Patent
Application |
20190103384 |
Kind Code |
A1 |
Feichtinger; Thomas ; et
al. |
April 4, 2019 |
Multi-LED System
Abstract
A multi-LED system is disclosed. In an embodiment a multi-LED
system includes a ceramic multilayer substrate in which at least
two ESD protection structures are integrated, at least two
light-emitting diodes arranged on the substrate and at least two
capping layers covering one of the light-emitting diodes.
Inventors: |
Feichtinger; Thomas; (Graz,
AT) ; Steinhauser; Stephan; (Ligist, AT) ;
Pudmich; Gunter; (Koflach, AT) ; Payr; Edmund;
(Graz, AT) ; Brunner; Sebastian; (Graz,
AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EPCOS AG |
Munchen |
|
DE |
|
|
Family ID: |
59814554 |
Appl. No.: |
16/086567 |
Filed: |
March 21, 2017 |
PCT Filed: |
March 21, 2017 |
PCT NO: |
PCT/EP2017/056687 |
371 Date: |
September 19, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 25/167 20130101;
H01L 27/0248 20130101; H01L 33/486 20130101; H01L 33/504 20130101;
H01L 33/0095 20130101; H01L 25/0753 20130101; H01L 33/641
20130101 |
International
Class: |
H01L 25/075 20060101
H01L025/075; H01L 25/16 20060101 H01L025/16; H01L 27/02 20060101
H01L027/02; H01L 33/50 20060101 H01L033/50; H01L 33/64 20060101
H01L033/64; H01L 33/48 20060101 H01L033/48 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2016 |
DE |
10 2016 105 578.6 |
Apr 22, 2016 |
DE |
10 2016 107 497.7 |
Claims
1-17. (canceled)
18. A multi-LED system comprising: a ceramic multilayer substrate
in which at least two ESD protection structures are integrated; at
least two light-emitting diodes arranged on the substrate; and at
least two capping layers covering one of the light-emitting
diodes.
19. The multi-LED system according to claim 18, wherein the capping
layers are embodied as light-conversion layers.
20. The multi-LED system according to claim 19, wherein a first
capping layer is embodied to produce warm-white light and a second
capping layer is embodied to produce cold-white light.
21. The multi-LED system according to claim 18, wherein each ESD
protection structure has ceramic layers and electrode layers
arranged therebetween, and wherein the electrode layers are
electrically connected via vias.
22. The multi-LED system according to claim 18, wherein the ESD
protection structures comprise a varistor ceramic.
23. The multi-LED system according to claim 18, wherein no further
electrical components are arranged on the substrate in addition to
the light-emitting diodes.
24. The multi-LED system according to claim 18, further comprising
a temperature monitoring component arranged on the substrate.
25. The multi-LED system according to claim 24, wherein the
temperature monitoring component is arranged between the
light-emitting diodes.
26. The multi-LED system according to claim 18, wherein the
multi-LED system comprises exactly two light-emitting diodes.
27. The multi-LED system according to claim 18, wherein the
multi-LED system comprises exactly four light-emitting diodes.
28. The multi-LED system according to claim 18, wherein first
external contacts and second external contacts are arranged on a
lower side of the substrate for each light-emitting diode.
29. The multi-LED system according to claim 28, wherein each ESD
protection structure has ceramic layers and electrode layers
arranged therebetween, wherein the electrode layers are
electrically connected via vias, and wherein the electrode layers
are electrically connected to the external contacts via the
vias.
30. The multi-LED system according to claim 28, wherein all
external contacts are arranged in a row.
31. The multi-LED system according to claim 28, wherein the
external contacts are arranged in a plurality of rows and
columns.
32. A method for producing the multi-LED system according to claim
18, the method comprising: sintering the substrate together with
the ESD protection structures.
33. The method according to claim 32, further comprising: attaching
the light-emitting diodes to an upper side of the sintered
substrate; and covering each light-emitting diode with a capping
layer.
34. The method according to claim 33, further comprising dicing
after covering the light-emitting diodes with the capping layer.
Description
[0001] This patent application is a national phase filing under
section 371 of PCT/EP2017/056687, filed Mar. 21, 2017, which claims
the priority of German patent application 10 2016 105 578.6, filed
Mar. 24, 2016 and German patent application 10 2016 107 497.7,
filed Apr. 22, 2016, each of which is incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a multi-LED system that is
embodied, in particular, to produce a flash. Such multi-LED systems
are required, in particular, for mobile applications such as
smartphones or digital cameras.
BACKGROUND
[0003] Multi-LED systems comprising a hybrid design made of a
substrate and an assembly of passive components and two
light-emitting diodes (LEDs) are known. The LEDs are covered by
light-conversion layers such that, for example, a combination of
warm-white light and of cold-white light is produced. This should
ensure improved illumination and more natural colors in the case of
flash photographs.
[0004] For the purposes of protecting the LEDs from electrostatic
discharges (ESDs), use can be made of discrete components with a
varistor function, although these lead to a larger installation
size. The document DE 10 2014 101 092 A1 discloses a chip with a
varistor function, on which an LED can be mounted.
SUMMARY OF THE INVENTION
[0005] Embodiments provide a multi-LED system with improved
properties.
[0006] The multi-LED system according to embodiments of the
invention has a ceramic multilayer substrate, in which at least two
ESD protection structures are integrated. At least two
light-emitting diodes are arranged on the substrate. In particular,
an integrated ESD protection structure is present for each
light-emitting diode. Furthermore, the multi-LED system has at
least two capping layers, wherein each capping layer covers one of
the light-emitting diodes.
[0007] Such a multi-LED system allows integration of a plurality of
LEDs, optics and an ESD protection in a very small space. In
particular, the multi-LED system can be used as a flashlight module
in mobile applications.
[0008] By way of example, the capping layers are embodied as
protection layers and/or as optically active layers. In particular,
the capping layers can be embodied to produce different
characteristics of the emitted light. Here, these can be
light-conversion layers. By way of example, one of the capping
layers is embodied to produce warm-white light and another of the
capping layers is embodied to produce cold-white light. In addition
or as an alternative thereto, the capping layers can also have a
lens function.
[0009] In one embodiment, no further electrical component is
arranged on the substrate in addition to the light-emitting diodes.
This facilitates particularly good miniaturization of the multi-LED
system.
[0010] Alternatively, one or more further electrical components can
also be arranged on the substrate, for example, a component for
monitoring the temperature. The component can be arranged between
the LEDs.
[0011] In one embodiment, the multi-LED system has exactly two
light-emitting diodes. By way of example, this is a dual LED flash
module. In another embodiment, the multi-LED system has a number of
n.times.n light-emitting diodes, where n is an integer greater than
1. By way of example, the light-emitting diodes can be arranged in
n rows and n columns. By way of example, the multi-LED system has
exactly four light-emitting diodes.
[0012] The LEDs can all be arranged in one row. Alternatively, the
LEDs can be arranged in a plurality of rows and columns, for
example.
[0013] First and second external contacts can be arranged on a
lower side of the substrate for each light-emitting diode. The
external contacts can all be arranged in one row. Alternatively,
the external contacts can be arranged in a plurality of rows and
columns. As a result, this may result in additional saving of
space.
[0014] Furthermore, a method for producing such a multi-LED system
is specified. According to the method, the substrate with the
integrated ESD protection structures is sintered. The
light-emitting diodes are attached to an upper side of the sintered
substrate in a further method step. Each light-emitting diode is
covered by a capping layer. In this way, it is possible to produce,
in particular, a multi-substrate that can be diced into a
multiplicity of multi-LED systems. In particular, dicing can be
implemented after the application of the capping layers.
[0015] A plurality of embodiments of the invention are described in
the present disclosure. All properties that are disclosed in
relation to the multi-LED system and the method are also disclosed
accordingly in relation to the other aspects, even if the
respective property is not explicitly mentioned in the context of
the other aspects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The subject matter described here is explained in more
detail below on the basis of schematic exemplary embodiments.
[0017] In detail:
[0018] FIG. 1 shows a schematic cross section of an embodiment of a
multi-LED system;
[0019] FIG. 2 shows a plan view on an upper side of an embodiment
of a multi-LED system;
[0020] FIG. 3 shows a plan view on a lower side of an embodiment of
a multi-LED system;
[0021] FIG. 4 shows a plan view on an upper side of a
multi-substrate comprising a multiplicity of multi-LED systems;
[0022] FIG. 5 shows a schematic cross section of a further
embodiment of a multi-LED system;
[0023] FIG. 6 shows a flowchart of a method for producing a
multi-LED system; and
[0024] FIG. 7 shows a flowchart of a further method for producing a
multi-LED system.
[0025] Preferably, the same reference signs in the following
figures refer to functionally or structurally corresponding parts
of the various embodiments.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0026] FIG. 1 shows a multi-LED system 1 comprising a substrate 2,
which is constructed as a multi-layer construct. The substrate 2
has a multiplicity of ceramic layers 3 that are stacked one above
the other. Two ESD protection structures 4, 4' are integrated into
the substrate 2. The ESD protection structures can also be referred
to as ESD protection components. The ceramic is a varistor ceramic,
in particular, for example, doped ZnO, SrTiO.sub.2 or SiC. By way
of example, the doping substances comprise antimony, bismuth and/or
praseodymium.
[0027] The varistor ceramic has a high thermal conductivity, for
example, greater than or equal to 20 W/mK. In particular, the
thermal conductivity can be 22 W/mK. In this way, produced heat
losses can be dissipated through the varistor ceramic. By way of
example, the substrate has a thickness in the range from 200 .mu.m
to 500 .mu.m, with this being the thickness of the ceramic without
metallizations on the lower and upper side 11, 12.
[0028] The ESD protection structures 4, 4' are each constructed
from the ceramic layers 3, in particular from portions of the
ceramic layers 3, and first electrode layers 5, 5' and second
electrode layers 6, 6' arranged therebetween. The first electrode
layers 5, 5' are embodied as meshing with the second electrode
layers 6, 6'. By way of example, the electrode layers 5, 5', 6, 6'
are formed from 100% Ag. The first and second electrode layers 5,
5', 6, 6' are electrically connected by first and second vias 7,
7', 8, 8'. The vias 7, 7', 8, 8' are through-contacts, in
particular metal vias. By way of example, the vias 7, 7', 8, 8' are
formed from 100% Ag.
[0029] The vias 7, 7', 8, 8' are electrically connected to first
and second external contacts 9, 9', 10, 10', which are arranged on
a lower side 11 of the substrate 2. By way of example, these are
contact pads. The external contacts 9, 9', 10, 10' can comprise
AgNiAu. Furthermore, the vias 7, 7', 8, 8' are electrically
connected to first and second connector contacts 12, 12', 13, 13',
which are arranged on an upper side 14 of the substrate 2.
[0030] Moreover, a glass layer 15 for protecting the varistor
ceramic is arranged on the upper side 14. By way of example, the
glass layer 15 has a TiO.sub.2 filler material. The connector
contacts 12, 12', 13, 13' are led through the glass layer 15. Such
a glass layer may also be present on the lower side 11.
[0031] Two LEDs 16, 16' are arranged on the substrate 2. The LEDs
16, 16' are electrically and mechanically connected to the
connector contacts 12, 12', 13, 13', for example, by solder 17,
17'. AuSn can be used to solder the material.
[0032] By way of example, the LEDs 16, 16' are embodied for flip
chip mounting. In particular, the LEDs 16, 16' each can have two
contact faces on their lower sides. The LEDs 16, 16' could also
each have respectively one first contact face on their lower side
and one second contact face on their upper side. The second contact
face can be connected to the substrate 2 by means of a wire, in
particular a gold wire. The LEDs 16, 16' can be also only contacted
with the substrate 2 by wires. The LEDs 16, 16' are each covered by
a capping layer 18, 18'. The capping layers 18, 18' can be embodied
as protection layers for protecting the LEDs 16, 16' and/or as
optically active layers. By way of example, the capping layers 18,
18' are embodied as lenses and/or light-conversion layers. The
capping layers 18, 18' can have different embodiments. By way of
example, the first capping layer 18 is embodied such that the light
produced by the first LED 16 obtains a cold-white light
characteristic and the second capping layer 18' is embodied such
that the light produced by the second LED 16' obtains a warm-white
light characteristic. Consequently, the capping layers 18, 18'
serve to shift the light spectrum. By way of example, the capping
layers are each embodied as phosphor layers, in particular with a
silicone matrix. By way of example, the capping layers 18, 18' have
a red or yellow color.
[0033] In addition or as an alternative thereto, the capping layers
18, 18' can also have a lens function. In this case, the capping
layers 18, 18' can also be embodied in colorless fashion.
[0034] By way of example, the multi-LED system 1 is used to produce
a flashlight. In one embodiment, the LED system 1 has no further
discrete components on the substrate 2 in addition to the LEDs 16,
16'. This facilitates a particularly good miniaturization of the
LED system 1. Moreover, this can improve the light yield and the
homogeneity of the emitted light. In particular, there is no
shadowing or color change as a result of further surface-mounted
components.
[0035] FIG. 2 shows a plan view on an upper side 14 of a multi-LED
system 1. By way of example, the multi-LED system 1 is embodied
like in FIG. 1.
[0036] The LEDs 16, 16' are each covered by capping layers 18, 18'.
The capping layers 18, 18' have an approximately square form. The
capping layers 18, 18' do not extend over the entire upper side 14
of the substrate 2 such that part of the glass layer 15 is
exposed.
[0037] By way of example, the multi-LED system 1 has dimensions of
less than or equal to 2.times.4 mm.sup.2. By way of example, the
dimensions are 1.times.2 mm.sup.2. By way of example, the
dimensions can also be 1.7.times.3.4 mm.sup.2. As a result, the
multi-LED system 1 has substantially smaller dimensions than
conventional systems.
[0038] FIG. 3 shows a plan view on a lower side 11 of the multi-LED
system 1. By way of example, this is the multi-LED system 1 from
FIG. 2.
[0039] The lower side 11 of the substrate 2 is covered by a glass
layer 19. The glass layer 19 can be embodied like the glass layer
15 arranged at the upper side 14 (see FIG. 2).
[0040] The multi-LED system 1 has four external contacts 9, 9', 10,
10'. By way of example, the external contacts 9, 10 are embodied to
connect the first LED 16 and, unlike what is illustrated in FIG. 1,
they are arranged in succession. The external contacts 9', 10' are
embodied to connect the second LED 16' and are likewise arranged in
succession. Consequently, the external contacts 9, 9', 10, 10' are
arranged in the form of a plurality of rows and columns. This
facilitates a good electric contact with low spatial requirements.
Furthermore, the first external contacts 9, 9' each have a polarity
mark 20, 20'.
[0041] FIG. 4 shows a plan view on an upper side of a
multi-substrate 21 comprising a multiplicity of multi-LED systems
1. After dicing, the multi-LED systems 1 are each embodied as
described in FIGS. 1 to 3, for example.
[0042] By way of example, the multi-substrate 21 has 325 multi-LED
systems 1. By way of example, the multi-substrate 21 has a diameter
in the range of 2 inches to 4 inches. By way of example, the
multi-substrate 21 has dimensions of 54.5.times.54.5 mm.sup.2.
[0043] FIG. 5 shows a sectional view of a further multi-LED system
1 according to the embodiments of the invention. In contrast to the
multi-LED system 1 shown in FIG. 1, this is a four-LED system,
i.e., exactly four LEDs 16, 16', 16'', 16''' are present.
Furthermore, in contrast to FIG. 1, a temperature monitoring
component 22 is arranged on the substrate 2. By way of example,
this is an NTC or PTC thermistor. The temperature monitoring
component 22 is electrically connected to connector contacts 25, 26
on the lower side 11 of the substrate 2 by means of vias 23,
24.
[0044] An ESD protection structure 4, 4', 4, 4''' that is
integrated in the substrate 2 is provided for each LED 16, 16',
16'', 16'''. Each LED 16, 16', 16'', 16''' is covered by a capping
layer 18, 18', 18'', 18'''. The capping layers 18, 18', 18'', 18'''
can all have different embodiments. By way of example, two capping
layers 18, 18' and 18'', 18''', respectively, may also have the
same properties in each case. By way of example, the two centrally
arranged capping layers 18', 18'' have the same properties and the
two capping layers 18, 18''' arranged on the outside have the same
properties.
[0045] As imaged, the LEDs 16, 16', 16'', 16''' can be arranged
next to one another. Alternatively, the LEDs 16, 16', 16'', 16'''
can also be arranged at the corners of a rectangle such that two
LEDs are arranged next to one another in each case and two LEDs are
arranged behind one another in each case. Consequently, the LEDs
are arranged in a plurality of rows and columns. Accordingly, the
connector contacts can be arranged similarly to what is shown in
FIG. 3.
[0046] FIG. 6 shows the flowchart of a method for producing a
multi-LED system. By way of example, the multi-LED system obtained
is embodied as described in FIGS. 1 to 5. During the production,
the multi-substrate described in FIG. 4 is obtained first, for
example, and it is subsequently diced.
[0047] According to the method, the following steps are carried out
in succession: cutting the green sheets to size (step A; "tape
cutting"), printing the sheets with a metal paste in order to form
the electrode layers (step B; "sheet printing"), laminating the
printed sheets (step C; "sheet laminating"), drilling holes through
the sheet stack for the vias by means of a laser (step D; "via
drilling with laser"), filling the holes with a metal paste (step
E; "via filling"), isostatic pressing (step F; "isostatic
pressing"), cutting the stack to size (step G; "stack cutting"),
sintering the stack (step H; "sintering"), producing external
contacts and connector contacts by printing the upper and lower
sides of the substrate (step I.sub.1; "metal screen printing top
& bottom"), firing (step J.sub.1; "firing"), printing a glass
paste on the upper and lower side (step K.sub.1; "glass screen
printing top & bottom"), plating (step L.sub.1; "plating"),
mounting the LEDs (step M.sub.1; "LED mounting"), soldering the
LEDs with AuSn soldering material (step N.sub.1; "AuSn reflow
soldering"), applying the capping layers acting as a lens (step O;
"lens attach+curing") and dicing (step P; "dicing").
[0048] FIG. 7 shows the flowchart of a further method for producing
a multi-LED system. The method steps listed on the left-hand side
in the flowchart up to the sintering of the substrate (step H)
correspond to the method steps described in FIG. 6.
[0049] Subsequently, the following method steps are carried out for
applying the contacts and discrete components: applying and
structuring a photoresist (step 12; "photoresist structuring"),
baking the photoresist (step J.sub.2; "baking"), sputtering on a
metal layer (step K.sub.2; "sputtering"), chemical ablation (step
L.sub.2; "chemical lift-off"), applying the LEDs and the
temperature monitoring component (step M.sub.2; "LED and NTC
mounting"), eutectic bonding with AuSn (step N.sub.2; "AuSn
eutectic bonding"), applying the capping layers acting as a lens
(step O; "lens attach+curing") and dicing (step P; "dicing").
[0050] The description of the subject matter described here is not
restricted to the individual special embodiments. Rather, the
features of the individual embodiments can be combined with one
another, provided this is technically advantageous.
* * * * *